/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.code.or.common.glossary;

import com.google.code.or.common.util.ToStringBuilder;

/**
 * 
 * @author Jingqi Xu
 */
public final class Pair<T> {
	//
	private T before;
	private T after;
	
	/**
	 * 
	 */
	public Pair() {
	}
	
	public Pair(T before, T after) {
		this.before = before;
		this.after = after;
	}
	
	/**
	 * 
	 */
	public String toString() {
		return new ToStringBuilder(this)
		.append("before", before)
		.append("after", after).toString();
	}
	
	/**
	 * 
	 */
	public T getBefore() {
		return before;
	}

	public void setBefore(T before) {
		this.before = before;
	}
	
	public T getAfter() {
		return after;
	}

	public void setAfter(T after) {
		this.after = after;
	}
	
	/**
	 * 
	 */
	public void swap() {
		final T t = this.before;
		this.before = this.after;
		this.after = t;
	}
	
	/**
	 * 
	 */
	public static void swap(Pair<?> p) {
		doSwap(p); // Nothing but capture the <?>
	}
	
	private static <T> void doSwap(Pair<T> p) {
		synchronized(p) {
			final T t = p.before;
			p.before = p.after;
			p.after = t;
		}
	}
}
